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J/ApJ/607/60        FIRST-2MASS faint sources                (Glikman+, 2004)

FIRST-2MASS sources below the APM detection threshold: a population of highly reddened quasars. Glikman E., Gregg M.D., Lacy M., Helfand D.J., Becker R.H., White R.L. <Astrophys. J., 607, 60-75 (2004)> =2004ApJ...607...60G
ADC_Keywords: QSOs ; Infrared sources ; Radio sources ; Redshifts Photometry, photographic ; Photometry, infrared Keywords: dust, extinction - quasars: general - surveys Abstract: We have constructed a sample of bright near-infrared sources that are detected at radio wavelengths but undetected on the first-generation Palomar Observatory Sky Survey (POSSI) plates in order to search for a population of dust-obscured quasars. Optical and infrared spectroscopic follow-up of the sample has led to the discovery of 17 heavily reddened quasars (B-K>6.5), 14 of which are reported here for the first time. This has allowed us to define a region in the R-K, J-K color plane in which 50% of the radio-selected objects are highly reddened quasars. We compare the surface density of this previously overlooked population to that of ultraviolet-excess radio-selected quasars, finding that they make up ∼20% of the total quasar population for K≲15.5. Description: Spectroscopy of our candidate quasars was carried out in the optical and near-infrared at four different observatories. The majority of the optical spectra were obtained at the 10m Keck telescopes by using the ESI and, to a lesser extent, LRIS spectrographs. Optical spectra were also obtained at the 3m Shane telescope at Lick Observatory. Near-infrared spectroscopy was performed at the NASA Infrared Telescope Facility (IRTF) by using SpeX and at the MDM Observatory on Kitt Peak by using the TIFKAM infrared camera in spectroscopic mode. We also obtained seven spectra from the Sloan Digital Sky Survey Spectral database. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 105 69 Optically faint FIRST-2MASS red quasar candidates
See also: VIII/71 : The FIRST Survey Catalog, Version 03Apr11 (Becker+ 2003) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) I/271 : The Guide Star Catalog, Version 2.2 (GSC2.2) (STScI, 2001) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 2 I2 h RAh Right ascension (J2000.0) from FIRST catalog 4- 5 I2 min RAm Right ascension (J2000.0) from FIRST catalog 7- 11 F5.2 s RAs Right ascension (J2000.0) from FIRST catalog 13 A1 --- DE- Declination sign (J2000.0) from FIRST catalog 14- 15 I2 deg DEd Declination (J2000.0) from FIRST catalog 17- 18 I2 arcmin DEm Declination (J2000.0) from FIRST catalog 20- 23 F4.1 arcsec DEs Declination (J2000.0) from FIRST catalog 24 A1 --- Note [c] Individual note (1) 25 A1 --- l_Bmag Limit flag on Bmag 26- 30 F5.2 mag Bmag GCS2 B magnitude 32 A1 --- l_Rmag Limit flag on Rmag 33- 37 F5.2 mag Rmag GCS2 R magnitude 39- 43 F5.2 mag Jmag 2MASS J magnitude 45- 49 F5.2 mag Hmag 2MASS H magnitude 51- 55 F5.2 mag Ksmag 2MASS Ks magnitude 57- 62 F6.2 mJy Fpeak FIRST 20cm peak flux density 64- 70 F7.2 mJy Fint FIRST 20cm integrated flux density 72- 75 F4.2 mag J-K J-K colour index 77 A1 --- l_R-K Limit flag on R-K 78- 81 F4.2 mag R-K R-K colour index (R magnitude from GSC 2) 83- 87 F5.3 --- z ? Redshift 88 A1 --- n_z [e] Note on z (2) 90-100 A11 --- Type Type of object 102 I1 --- Ref [1/3]? Reference (3) 103 A1 --- n_Ref [bd] Note on Ref (4)
Note (1): c: This object had a FIRST-APM separation of 5.77" and was identified as an extended source by the APM machine's scans of both the O and E plates. These data gave the objects a 54% probability of being associated with each other. Our criterion of 94% reliability, discussed in Sect. 2, allowed this source to remain a candidate. Its extended radio morphology, as well as optical magnitudes and spectrum, suggest that this object is the contaminant allowed by our survey statistics. Note (2): e: We determined the redshift from Hα, which lies between the H and K bands; its signal was strong enough to be detected in the region of telluric absorption. We also used a weaker Hβ line also residing in the telluric absorption region between J and H. This allowed us to identify Mg II absorption in the optical spectrum at this same redshift. Smith et al. (2002, Cat. J/ApJ/569/23) obtained an independent redshift measurement of z=1.800 for this object using Hα alone. Note (3): References as follows: 1 = Gregg et al. 2002, Cat. J/AJ/112/407 2 = Smith et al. 2002, Cat. J/ApJ/569/23 3 = Lacy et al., 2002AJ....123.2925 Note (4): Notes as follows: b = SDSS optical spectrum d = This object was initially classified as an emission-line galaxy, based on its optical spectrum. The near-infrared spectrum reveals a red continuum and a broad Paβ line. See Sect. 4 for further discussion.
History: From electronic version of the journal
(End) James Marcout, Patricia Vannier [CDS] 06-Jul-2004
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